Most photographs are produced by: exposing a film to light; developing the film to produce a negative; and processing (printing) the negative to produce a photographic print. The dark areas in the negative allow little light to pass so that the tones in the print appear light as they did in the original scene. Also the negatives from most color films have an overall orange color, and are smaller than the print. Thus, even when the negatives and prints for one or more processed rolls of film are together, it is difficult for an amateur photographer who is not trained to view photographic negatives to determine the negative that was used to produce a specific print.
An amateur photographer may receive the negatives and prints for one or more rolls of processed film in an envelope having two compartments. The negatives are usually placed in one compartment and the prints are usually placed in the other compartment. Some of the prints may be: given away; placed in a photo album; framed; or become separated from the negatives. The envelopes maybe haphazardly thrown in a box and mixed with other envelopes in the box. Thus, when someone wants to order reprints or enlargements of one or more prints it may be difficult to locate the negatives that correspond to the prints that they want to order.
When the prints and negatives are packaged together in an envelope, the negatives are susceptible to scratching and contamination from dust, dirt and/or fingerprints because the envelope does not provide a damage-free environment for the negatives. The various forms of negative damage mentioned above will reduce the quality of the reprints and enlargements that are made from the negatives.
Sometimes an amateur photographer or the photofinisher places the negatives in wax or plastic sleeves to protect and store the negatives and accidentally damages the negatives as they are inserted into the sleeves. This provides protection for the negatives but does not provide for easy identification of the negatives. In the past contact prints have been made to provide a convenient way to identify negatives by providing a page of positive images that have the same size on the contact print as the negative images on the film. This is done by cutting a length of negatives into individual strips. The strips are then arranged on a sheet of photographic paper or placed in transparent sleeves and then held in contact with the photographic paper with a glass plate, negative holder or negative gate, etc. An alternative method of producing sheets that contain images of the negatives involves optical printing. Multiple negatives are placed in a negative holder and are exposed on photosensitive paper with a photographic enlarger or photographic printer. This technique would allow reduction or enlargement of the images or images appearing on the paper by changing the magnification of the enlargement lens. Typically, the above sheets, referred to as proof sheets or index sheets were stored in a binder interleaved with sleeved negatives. Often times the negatives were printed while the negatives were in a transparent sleeve.
During the exposure of the index print, a group of negatives are simultaneously exposed with an amount of light that represents the average requirements of the group of negatives. This technique provides no opportunity to correct for the exposure requirement of individual negatives. An alternate technique to optically produce index prints uses a cluster lens array with each lens equipped with a shutter mechanism.